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Date: Thu, 16 Jun 2016 17:10:49 +0200
From: Michal Hocko <mhocko@kernel.org>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Rik van Riel <riel@redhat.com>, Mel Gorman <mgorman@suse.de>,
        "Huang, Ying" <ying.huang@intel.com>, Minchan Kim <minchan@kernel.org>,
        Vinayak Menon <vinmenon@codeaurora.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 1/2] Revert "mm: make faultaround produce old ptes"
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On Thu 16-06-16 15:27:35, Kirill A. Shutemov wrote:
> On Thu, Jun 16, 2016 at 02:20:02PM +0200, Michal Hocko wrote:
> > On Tue 14-06-16 11:42:29, Kirill A. Shutemov wrote:
> > > This reverts commit 5c0a85fad949212b3e059692deecdeed74ae7ec7.
> > > 
> > > The commit causes ~6% regression in unixbench.
> > 
> > Is the regression fully explained? My understanding from the email
> > thread is that this is suspiciously too high. It is not like I would
> > be against the revert but having an explanation would be really
> > appreciated.
> 
> My understanding is that it's overhead on setting accessed bit:
> 
> http://lkml.kernel.org/r/20160613125248.GA30109@black.fi.intel.com

But those numbers cannot explain the regression completely AFAIU. It
smells like something else is going on. Anyway, as I've said I do not
have anything against the revert just more than "unixbench regresses"
would be nice.
-- 
Michal Hocko
SUSE Labs